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<a name="PowerPC-Embedded-1"></a>
<h4 class="subsection">21.3.5 PowerPC Embedded</h4>

<a name="index-DVC-register"></a>
<p><small>GDB</small> supports using the DVC (Data Value Compare) register to
implement in hardware simple hardware watchpoint conditions of the form:
</p>
<div class="smallexample">
<pre class="smallexample">(gdb) watch <var>ADDRESS|VARIABLE</var> \
  if  <var>ADDRESS|VARIABLE</var> == <var>CONSTANT EXPRESSION</var>
</pre></div>

<p>The DVC register will be automatically used when <small>GDB</small> detects
such pattern in a condition expression, and the created watchpoint uses one
debug register (either the <code>exact-watchpoints</code> option is on and the
variable is scalar, or the variable has a length of one byte).  This feature
is available in native <small>GDB</small> running on a Linux kernel version 2.6.34
or newer.
</p>
<p>When running on PowerPC embedded processors, <small>GDB</small> automatically uses
ranged hardware watchpoints, unless the <code>exact-watchpoints</code> option is on,
in which case watchpoints using only one debug register are created when
watching variables of scalar types.
</p>
<p>You can create an artificial array to watch an arbitrary memory
region using one of the following commands (see <a href="Expressions.html#Expressions">Expressions</a>):
</p>
<div class="smallexample">
<pre class="smallexample">(gdb) watch *((char *) <var>address</var>)@<var>length</var>
(gdb) watch {char[<var>length</var>]} <var>address</var>
</pre></div>

<p>PowerPC embedded processors support masked watchpoints.  See the discussion
about the <code>mask</code> argument in <a href="Set-Watchpoints.html#Set-Watchpoints">Set Watchpoints</a>.
</p>
<a name="index-ranged-breakpoint"></a>
<p>PowerPC embedded processors support hardware accelerated
<em>ranged breakpoints</em>.  A ranged breakpoint stops execution of
the inferior whenever it executes an instruction at any address within
the range it specifies.  To set a ranged breakpoint in <small>GDB</small>,
use the <code>break-range</code> command.
</p>
<p><small>GDB</small> provides the following PowerPC-specific commands:
</p>
<dl compact="compact">
<dd><a name="index-break_002drange"></a>
</dd>
<dt><code>break-range <var>start-location</var>, <var>end-location</var></code></dt>
<dd><p>Set a breakpoint for an address range given by
<var>start-location</var> and <var>end-location</var>, which can specify a function name,
a line number, an offset of lines from the current line or from the start
location, or an address of an instruction (see <a href="Specify-Location.html#Specify-Location">Specify Location</a>,
for a list of all the possible ways to specify a <var>location</var>.)
The breakpoint will stop execution of the inferior whenever it
executes an instruction at any address within the specified range,
(including <var>start-location</var> and <var>end-location</var>.)
</p>
<a name="index-set-powerpc"></a>
</dd>
<dt><code>set powerpc soft-float</code></dt>
<dt><code>show powerpc soft-float</code></dt>
<dd><p>Force <small>GDB</small> to use (or not use) a software floating point calling
convention.  By default, <small>GDB</small> selects the calling convention based
on the selected architecture and the provided executable file.
</p>
</dd>
<dt><code>set powerpc vector-abi</code></dt>
<dt><code>show powerpc vector-abi</code></dt>
<dd><p>Force <small>GDB</small> to use the specified calling convention for vector
arguments and return values.  The valid options are &lsquo;<samp>auto</samp>&rsquo;;
&lsquo;<samp>generic</samp>&rsquo;, to avoid vector registers even if they are present;
&lsquo;<samp>altivec</samp>&rsquo;, to use AltiVec registers; and &lsquo;<samp>spe</samp>&rsquo; to use SPE
registers.  By default, <small>GDB</small> selects the calling convention
based on the selected architecture and the provided executable file.
</p>
</dd>
<dt><code>set powerpc exact-watchpoints</code></dt>
<dt><code>show powerpc exact-watchpoints</code></dt>
<dd><p>Allow <small>GDB</small> to use only one debug register when watching a variable
of scalar type, thus assuming that the variable is accessed through the
address of its first byte.
</p>
</dd>
</dl>

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